1. Field of the Invention
The present invention is related to a sunlight sensor, and more specifically, to a sunlight sensor used in the control of an air conditioner or other device.
2. Description of the Related Art
In the past, sunlight sensors, such as sunlight sensors used for air conditioner control in an automobile as disclosed in U.S. Pat. No. 3,268,185 and as shown in FIG. 81, have been known.
The sunlight sensor 1 in FIG. 81 is provided with a light-cutoff means 3, having a light-receiving hole 3a which is located over a light detector 2a so as to allow sunlight selectively to pass to the light detector 2a. Using a constant illuminated surface area upon which sunlight strikes light detector 2a, the amount of heat to which incident light is converted, which depends upon the angle of elevation of the incident sunlight, is obtained from the intensity of illumination light detector 2a.
In addition, there is a sunlight sensor as shown in FIG. 82, which was disclosed in Japanese Unexamined Patent Application Publication (Kokai) No. 2-216402.
The sunlight sensor 5 in FIG. 82, in addition to having a cover 6 of the required cover shape to cover the light-detection section, which is not shown, has, between cover 6 and the light-detection section, a diffuser 7. The cover 6 and diffuser 7 are used to control the intensity of illumination striking the light-detection section, to make the intensity correspond to the angle of elevation and direction of the sunlight.
However, in the sunlight sensor shown in FIG. 81, in the case of sunlight at a low angle of elevation, it is extremely difficult to keep the illuminated area of the light detector 2a the same as in the case of a high angle of elevation of the sunlight passing through the light cutoff means 3. For that reason, it is necessary to additionally provide a low-elevation-angle light detector 2b around the outside of light detector 2a, thereby causing the sunlight sensor 1 to be large and complex.
In addition, in the sunlight sensor of FIG. 82, the cover 6 is used to define the illumination level which corresponds to the sunlight elevation angle and direction at the light-detection section. However, in this case, in which a cover is provided at the top of the light-detection section, when the sun is directly overhead, the output of the light-detection section drops suddenly, making it impossible to produce the desired signal. For this reason, it is necessary to locate a diffuser 7 between cover 6 and the light-detection section, thus making the sunlight sensor 5 large and complex.
The present invention, in consideration of the above problems, has as its object the provision of a sunlight sensor of simple construction and small size, which is capable to detecting illumination intensity (sunlight thermal load) with respect to the orientation of the sunlight sensor with good accuracy.